Daniel Boone Br.
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開始行:
*Daniel Boone Br. [#q6ae9ad2]
**1.Field of application [#y14a0c54]
>The Daniel Boone Bridge of Route I-77 crosses U.S. Route 60 and one set of Penn Central railroad tracks in Kanawha County , West Virginia.
**2.Circumstances of repair [#ia85cb99]
>Fatigue cracks were reported in the girder web gap at the transverse cross bracing locations and in the coped webs of the longitudinal girders at the box beam connections in 1985 and 1986 after about 20 years of service.
**3.Types of structure [#z33cc07d]
>The structure is composed of multiple continuous longitudinal girders, transverse box beam caps ,and transverse cross bracing ([[Fig.1>#fig1]]). The girder flanges are continuous over and through the box beam cap ([[Fig.2>#fig2]]). The girder bottom flange is fillet welded to the box beam web at the slot ([[Fig.3>#fig3]]). The girder top and bottom flanges at the splice locations contain longitudinally welded filler plates under bolt connected cover plates ([[Fig.4>#fig4]]).No positive attachment is made between the transverse connection plate and the girder bottom flange or top flange (embedded in concrete). The transverse connection plate is fit snug with the girder compression flange and cut short of the girder tension flange.
>The web and flange plates of the box beams are A588 or A572 , grade 50, steel. The remainder of the structural steel is A36.
CENTER:&aname(fig1);&attachref(Daniel1.gif);&br;
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CENTER:Fig.1 Cross section of Daniel Boone Bridge.
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CENTER:&aname(fig2);&attachref(Daniel2.gif);&br;
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CENTER:Fig.2 View of the longitudinal girders supported by a transverse box beam cap.
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CENTER:&aname(fig3);&attachref(Daniel3.gif);&br;
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CENTER:Fig.3 View of the longitudinal girder bottom flange plate weld connected to the box beam cap web.
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CENTER:&aname(fig4);&attachref(Daniel4.gif);&br;
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CENTER:Fig.4 A longitudinally weld connected filler plate under a bolt connected cover plate, bottom flange.
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**4.Details of loading [#nb67255d]
>Fluctuating loads due to rail live load.
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**5.Description of damage [#leb89001]
>Fatigue cracks were found in the longitudinal girder web gaps at the transverse connection plate ([[Fig.5>#fig5]]) and in the longitudinal girder web cope at the connection with the box beam cap ([[Fig.6>#fig6]]).
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CENTER:&aname(fig5);&attachref(Daniel5.gif);&br;
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CENTER:Fig.5 Fatigue cracking along the girder web-flange fillet weld and at the transverse connection plate top end.
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CENTER:&aname(fig6);&attachref(Daniel6.gif);&br;
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CENTER:Fig.6 Coped longitudinal girder web at box beam cap connection.
&br;
>Causes of fatigue crack were as follows:
>In case of girder web gap.
-Out-of-plane distortion or bending of the girder web at the top web gaps caused by the differential displacement of the longitudinal girders.
-The lack of positive attachment between the embedded top flange and the transverse connection plate.
>In case of girder web cope.
-Differential movement between the longitudinal girders and the box beam caps.
**6.Repair method applied [#t02416f5]
>In case of the girder top web-flange fillet welds.
-The hole-drilling at all crack tips.
-The transverse connection plates were fillet weld connected to the compression flanges of the longitudinal girders and bolt connected on both sides with clip angles to the tension flanges of the longitudinal girders. In regions where the tension flange was the top flange, the concrete deck was chipped out for the insertion of the nut of the high strength bolt. After the bolt was installed, non-shrink grout was placed into the removed deck region.
&br;
>In case of the coped webs of the longitudinal girder connections.
-The short term retrofit was the hole-drilling at the crack tips.
-The long term retrofit was bolt connecting the top flanges of the longitudinal girders and the box beam caps with high strength bolts during a future deck replacement.
&br;
>Other case (Strengthening method applied)
-Peening the bottom flange plate tips on the box beam web in the high stress range regions.
-Peening the welded cover plate ends on the flange during a future deck replacement.
&br;
&br;
終了行:
*Daniel Boone Br. [#q6ae9ad2]
**1.Field of application [#y14a0c54]
>The Daniel Boone Bridge of Route I-77 crosses U.S. Route 60 and one set of Penn Central railroad tracks in Kanawha County , West Virginia.
**2.Circumstances of repair [#ia85cb99]
>Fatigue cracks were reported in the girder web gap at the transverse cross bracing locations and in the coped webs of the longitudinal girders at the box beam connections in 1985 and 1986 after about 20 years of service.
**3.Types of structure [#z33cc07d]
>The structure is composed of multiple continuous longitudinal girders, transverse box beam caps ,and transverse cross bracing ([[Fig.1>#fig1]]). The girder flanges are continuous over and through the box beam cap ([[Fig.2>#fig2]]). The girder bottom flange is fillet welded to the box beam web at the slot ([[Fig.3>#fig3]]). The girder top and bottom flanges at the splice locations contain longitudinally welded filler plates under bolt connected cover plates ([[Fig.4>#fig4]]).No positive attachment is made between the transverse connection plate and the girder bottom flange or top flange (embedded in concrete). The transverse connection plate is fit snug with the girder compression flange and cut short of the girder tension flange.
>The web and flange plates of the box beams are A588 or A572 , grade 50, steel. The remainder of the structural steel is A36.
CENTER:&aname(fig1);&attachref(Daniel1.gif);&br;
&br;
CENTER:Fig.1 Cross section of Daniel Boone Bridge.
&br;
CENTER:&aname(fig2);&attachref(Daniel2.gif);&br;
&br;
CENTER:Fig.2 View of the longitudinal girders supported by a transverse box beam cap.
&br;
&br;
CENTER:&aname(fig3);&attachref(Daniel3.gif);&br;
&br;
CENTER:Fig.3 View of the longitudinal girder bottom flange plate weld connected to the box beam cap web.
&br;
CENTER:&aname(fig4);&attachref(Daniel4.gif);&br;
&br;
CENTER:Fig.4 A longitudinally weld connected filler plate under a bolt connected cover plate, bottom flange.
&br;
**4.Details of loading [#nb67255d]
>Fluctuating loads due to rail live load.
&br;
**5.Description of damage [#leb89001]
>Fatigue cracks were found in the longitudinal girder web gaps at the transverse connection plate ([[Fig.5>#fig5]]) and in the longitudinal girder web cope at the connection with the box beam cap ([[Fig.6>#fig6]]).
&br;
CENTER:&aname(fig5);&attachref(Daniel5.gif);&br;
&br;
CENTER:Fig.5 Fatigue cracking along the girder web-flange fillet weld and at the transverse connection plate top end.
&br;
CENTER:&aname(fig6);&attachref(Daniel6.gif);&br;
&br;
CENTER:Fig.6 Coped longitudinal girder web at box beam cap connection.
&br;
>Causes of fatigue crack were as follows:
>In case of girder web gap.
-Out-of-plane distortion or bending of the girder web at the top web gaps caused by the differential displacement of the longitudinal girders.
-The lack of positive attachment between the embedded top flange and the transverse connection plate.
>In case of girder web cope.
-Differential movement between the longitudinal girders and the box beam caps.
**6.Repair method applied [#t02416f5]
>In case of the girder top web-flange fillet welds.
-The hole-drilling at all crack tips.
-The transverse connection plates were fillet weld connected to the compression flanges of the longitudinal girders and bolt connected on both sides with clip angles to the tension flanges of the longitudinal girders. In regions where the tension flange was the top flange, the concrete deck was chipped out for the insertion of the nut of the high strength bolt. After the bolt was installed, non-shrink grout was placed into the removed deck region.
&br;
>In case of the coped webs of the longitudinal girder connections.
-The short term retrofit was the hole-drilling at the crack tips.
-The long term retrofit was bolt connecting the top flanges of the longitudinal girders and the box beam caps with high strength bolts during a future deck replacement.
&br;
>Other case (Strengthening method applied)
-Peening the bottom flange plate tips on the box beam web in the high stress range regions.
-Peening the welded cover plate ends on the flange during a future deck replacement.
&br;
&br;
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